Switching device

ABSTRACT

A switching device has an openable contact arrangement including at least one movable contact member disposed on a movable contact arm and at least one stationary contact member. At least one movable braking body is provided for limiting the movement of the contact arm in opening the contact arrangement. The inertias of the contact arm with the movable contact member and the braking body are designed so that the contact arm is braked and the braking body is moved upon an impact of the contact arm with the braking body.

FIELD OF THE INVENTION

The present invention relate to a switching device having a contactarrangement having at least one movable contact member arranged on arotatable or displaceable contact arm and at least one stationarycontact member.

BACKGROUND INFORMATION

German Patent No. 37 25 860 A1 describes a power circuit-breaker havinga contact arrangement including a movable contact member arranged on arotatable contact arm and a stationary contact member, with a stop beingprovided to limit the movement of the contact arm in opening the movablecontact member. When the contact arm has reached its end position, thearm is prevented from dropping back into the closed position of thecontact arrangement by a suitable mechanical gripping device. Onedisadvantage of such a switching device is that there is the risk whenopening the contact arrangement that the contact arm might be thrownback by the stop, especially at high switching capacities, before themechanical gripping device is operative, so the contact arrangement isunintentionally closed again. There are switching devices, where thestop is provided with a damping layer, so some of the impact energy isabsorbed. However, it has not been possible previously to prevent recoilof the contact member at a reasonable cost. Instead, the rate of recoilof the contact arm is simply reduced by the damping layer.

French Patent No. 1,048,980 A describes a switching device according tothe definition of the species having a contact arrangement having amovable contact member arranged on a contact arm and a stationarycontact member, where the switching device includes a stop in the formof a movably arranged braking body that limits the movement of thecontact arm in opening the contact arrangement. After impact, thecontact arm moves together with the damping buffer belonging to thebraking body until it is braked. There is still the risk here that acontact arm striking with a high energy might be thrown back due to theelasticity of the damping buffer made of cured rubber or an equivalentmaterial.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a switchingdevice where the contact arm is braked on reaching its defined endposition even in the case of high switching capacities, without thenbeing thrown back by the stop.

The present invention includes a first stop in the form of movablyarranged braking body. The first stop is movable as a whole, and theinertias of a contact arm including a movable contact member the brakingbody that are relevant for impact are approximately equal so that animpact is executed when the contact arm strikes the braking body, sothat the contact arm is braked and the braking body is moved. Thepresent invention employs a concept of using a movable braking body as astop whose material and inertia (i.e., inert mass or moment of inertia)are matched to the contact arm so that when the contact arm strikes thebraking body, there is an impact such that the contact arm is stronglybraked and the braking body is displaced in a defined direction at acorresponding speed.

The braking body may optionally then be braked by suitable additionalmeans, e.g., a second stop or a spring, after reaching a defineddistance. In an advantageous embodiment of the present invention wherethe braking body is braked by a second stop, a damping body is providedbetween the braking body and the second stop, braking the movement ofthe switch arm after it collides with the braking body, if the brakingbody is in turn moved back into its starting position. This damping bodycan preferably be used at the same time as a holding element for thebraking body. In order for the contact arm not to be struck again by thebraking body moving backwards and thus be swung back, it has provenadvantageous for the braking body to have a return stop.

In other advantageous embodiments of the present invention, anelastically or plastically deformable material such as lead is used forthe braking body. In the latter case, a large portion of the energy ofmotion of the contact arm can thus be absorbed permanently as soon asthe contact member strikes the braking body. In such an embodiment, thepermanent deformation of the braking body can also easily be utilized(e.g., by using an inspection window or a pressure sensor, etc.) todisplay the lifetime of the switching device.

It is advantageous for the braking body to be supported by a guide sothat it moves in the direction of impact after impact with the contactarm.

In an advantageous embodiment of the present invention, the switchingdevice is one pole of a power circuit-breaker having two stationarycontact members and two movable contact members per pole to be switched,with the movable contact members being attached to the two opposite endsof the contact arm and one braking body being provided for each end ofthe contact arm. Finally, it is expedient if the contact arm can bepivoted about a centrally positioned axis or if the contact arm islinearly movable.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional details and advantages of the present invention are may beunderstood from the discussion which follows, with reference to thedrawings, in which:

FIG. 1 shows a side view of the contact arrangement of a switchingdevice according to the present invention having two rotatable contactmembers arranged on one contact arm and two braking bodies opposite theends of the contact arm, with the contact arrangement being in itsclosed position;

FIG. 2 shows the detail labeled as II in FIG. 1, with the braking bodybeing mounted in a damping body;

FIG. 3 shows a switching device according to the present inventionhaving a return stop to limit the rebound movement of the braking body;

FIG. 4 shows a side view of another embodiment of the present invention,with the braking body being arranged displaceably at an angle of about45° to the movement of the contact arm and;

FIG. 5 shows a section through one embodiment of the present invention,where the braking body is made of a plastically deformable material.

DETAILED DESCRIPTION

FIG. 1 shows a power circuit-breaker 1 including an interrupter chambercasing having a casing wall 2, which is indicated only schematically,and a contact arrangement 3 arranged in the casing. Two terminals 4, 5are provided for connecting power circuit-breaker 1 to a suitableelectric circuit and are connected by rail conductors 6, 7 in the formof a loop to two stationary contact members 8, 9. Stationary contactmembers 8, 9 are bridged by a contact arm 11 rotatable about an axis 10.Both arm halves 12, 13 of rotatable contact arm 11 press againststationary contact members 8, 9 by way of movable contact members 14,15. A braking body (first stop) 16, 17 is arranged between casing wall 2and the two sides of contact arm 11 opposite movable contact members 14,15. The braking bodies are made, for example, of the same material(e.g., copper) as the contact arm. The masses of both braking bodies 16,17 are matched to the mass of contact arm 11 including movable contactmembers 14, 15 so that an elastic impact is executed with an openingmovement in the direction indicated by arrows 100 when contact arm 11strikes respective braking body 16, 17, so that contact arm 11 isstrongly braked (ideally braked completely) and respective braking body16, 17 is displaced toward casing wall 2 at a corresponding rate. Casingwall 2 is designed as a second stop 18, 19 for braking the braking bodyin the impact area of respective braking body 16, 17. As shown in FIG.2, respective braking body 16, 17 is preferably mounted in a dampingbody 20 made of a flexible material (preferably rubber) whose movementis partially braked after impact of contact arm 11 against braking body16, 17. To prevent contact arm 11 from being swung back again by brakingbodies 16, 17 moving back, it has proven advantageous to provide areturn stop for respective braking body 16, 17. FIG. 3 shows acorresponding embodiment of a return stop 21, where the return stop isformed by the inside step of a step recess of a corresponding carrierpart 22.

The present invention is of course not limited to the embodimentsdescribed here. For example, the contact arm can be braked by a movablebraking body not only when using rotatable contact arms but also whenusing displaceable contact arms. Furthermore, a spring having acorresponding characteristic may also be used as the damping body. Inaddition, the respective braking body need not be arranged in the areaof the ends of the contact arm, as shown in the figures, but inparticular with regard to implementation of a straight central impact ofthe impacting body with the impacted body, it may be arranged so thatthe direction of impact coincides with the line connecting the midpoints of the contact arm (or contact arm half) and the braking body.

The braking body need not necessarily be displaced in the direction ofthe opening movement of the contact arm, but instead it may also move inanother direction, should this be necessary for reasons of space, forexample. FIG. 4 illustrates such an embodiment, showing a contact arm11′ which can pivot about an axis 10′; in its opening movement, itstrikes against a braking body 16′ supported by a guide 23 in such a waythat it is displaced obliquely outward along guide 23.

Furthermore, the material of the braking body need not necessarily beonly an elastically deformable material. Instead, the braking body mayalso be at least partially plastically deformable. Lead, for example,may be used as the material in this case. Therefore, a large portion ofthe energy of motion of the contact arm is absorbed permanently as soonas the contact member strikes the braking body. In such an embodiment,the permanent deformation of the braking body can also easily beutilized to display the lifetime of the switching device. FIG. 5 shows acorresponding embodiment of an arrangement having a braking body made ofa plastically deformable material. Contact arm 24 is indicated onlyschematically, and plastically deformable braking body 25 is also shown.A deformation space 26 into which the braking body can yield (dottedline) when the contact arm strikes is provided on the side facing awayfrom contact arm 24.

What is claimed is:
 1. A switching device comprising: an openablecontact arrangement including at least one movable contact memberdisposed on a movable contact arm and including at least one stationarycontact member; and at least one movable braking body for limiting amovement of the contact arm in opening the contact arrangement; a firstinertia of the contact arm and the movable contact member together beingapproximately equal to a second inertia of the at least one braking bodyso as to brake the contact arm and move the braking body upon an impactof the contact arm with the braking body.
 2. The switching device asrecited in claim 1 wherein the contact arm is at least one of rotatableand displaceable.
 3. The switching device as recited in claim 1 whereinthe contact arm is pivotable about a central axis.
 4. The switchingdevice as recited in claim 1 further comprising a braking device forbraking a movement of the braking body caused by the impact with thecontact arm and then moving the braking body into a starting position.5. The switching device as recited in claim 4 wherein the braking deviceincludes at least one of a stop, a spring and a stationary damping body.6. The switching device as recited in claim 4 further comprising areturn stop (21) for limiting a movement of the braking body in adirection of the contact arm.
 7. The switching device as recited inclaim 1 wherein the braking body includes an elastically deformablematerial.
 8. The switching device as recited in claim 1 wherein thebraking body includes a plastically deformable material for permanentlyabsorbing a major portion of an energy of motion of the contact arm inthe impact of the contact arm with the braking body.
 9. The switchingdevice as recited in claim 1 further comprising a guide for supportingthe braking body so as to enable the braking body to move in a directionof the impact after the impact with the contact arm.
 10. The switchingdevice as recited in claim 1 wherein the switching device is included ina pole of a power circuit-breaker, the at least one stationary contactmember including two stationary contact members, the at least onemovable contact member including two movable contact members, the atleast one braking body including two braking bodies, the two movablecontact members being disposed on opposite ends of the contact arm andthe two braking bodies being associated with the opposite ends of thecontact arm.